1. Field of Invention
The present invention pertains to the field of displays for electronic systems. More particularly, this invention relates to a low cost low pin count serial display drive mechanism for electronic systems.
2. Art Background
Prior electronic systems that perform relatively complex functions commonly employ highly integrated specialized integrated circuit chips. Typically, such specialized integrated circuit chips are designed and optimized for performing the required specialized function. For example, prior communication systems typically employ one or more specialized integrated circuit chips that perform functions required by a particular communication protocol.
One such specialized integrated circuit chip is the AM79C981 Ethernet control chip manufactured by Advanced Micro Devices, Inc. of Sunnyvale, Calif. This highly integrated and specialized control chip implements the communication functions required to perform communication repeater functions for a set of ethernet communication links.
In addition, prior electronic systems such as communication repeater hubs commonly provide a status display mechanism. Such a status display mechanism usually provides a variety of application specific indicators according to the specific requirements of the electronic system. For example, a status display for a communication repeater hub typically provides link activity indicators for the individual communication links.
Prior lower cost electronic systems usually provide such application specific indications via a set of illuminating elements such as light-emitting diodes (LEDs). For example, prior communication repeater hubs usually provide a set of communication link status indicator lights in the form of LEDs.
Typically, such application specific status information is maintained by the specialized integrated circuit chips. Such specialized chips typically supply the status information to the status display on a continuous basis for display. In addition, prior specialized integrated circuit chips commonly use serial data streams to supply data to the status display indicators.
For example, the AM79C981 Ethernet control chip generates a serial data stream that carries the status information for the corresponding communication links. The AM79C981 Ethernet control chip also generates a continuous clock signal and a strobe signal for externally latching and holding the contents of the serial data. Prior repeater hubs that employ the AM89C981 usually include a shift register that assembles the serial data stream under control of the continuous clock and also provide latch circuit that holds the status information under control of the strobe signal. Typically, the strobe signal periodically loads the latch from the Q outputs of the shift register such that the output of the latch drives the LEDs that provide the status display.
Unfortunately, such external shift register and external latch components usually increases the overall cost of such a communication repeater hub. Moreover, extra input/output pins are usually required on the control chip to provide the serial data stream, the serial clock, and the strobe signal. Such extra input/output pins usually increase the manufacturing costs of such highly integrated control chips. In addition, such extra pins may not be available without implementing the control chip in a higher pin count package that is much more expensive than would otherwise be necessary.